In a centrifugal compressor, a gas is extracted in a radial direction of a rotating impeller and the gas is compressed by a centrifugal force generated when the gas is extracted. As the centrifugal compressor, a multi-stage centrifugal compressor is known, in which impellers are provided in multiple stages in the axial direction and a gas is compressed stepwise.
In the centrifugal compressor, there is a structure having a casing which can be divided by a division surface spreading in a horizontal direction. The casing is configured of an upper half casing and a lower half casing. The upper half casing is placed on the lower half casing installed on a floor surface so as to be fastened by a bolt or the like, and thus, the casing is configured. In the centrifugal compressor, a rotor is disposed to penetrate the casing. The rotor is rotatable with respect to the casing.
For example, Patent Document 1 discloses a casing which can be divided in a vertical direction. In this casing, a gap between flange bolts fastening and fixing a first casing which is an upper half casing and a second casing which is a lower half casing is adjusted. Accordingly, leakage of a high-pressure gas from division surfaces of the first casing and the second casing is suppressed.
In the above-described casing, both ends in the axial direction are opened such that the rotor is inserted into the casing. In the opening portions, a seal device such as a labyrinth seal which seals between the opening portions and the rotor is provided. The seal device is attached to a housing, and thus, the seal device is indirectly fixed to the casing. Accordingly, a seal member such as an O ring is also provided on an outer peripheral surface of the housing in order to suppress leakage of a working fluid from a portion between the outer peripheral surface and the upper half casing and a portion between the outer peripheral surface and the lower half casing.